OVERVIEW

Why learn iOS programming?Share first-hand experience.Identify platform differences.Identify similarities with .NET

•Microsoft MVP for 4 years

•C#, WinForms, WPF, Silverlight

• Joined Cynergy about 2 years ago

•Working in native iOS ever since

•iJoshSmith.com (my iOS blog)

MY BOOK

iOS Programming for .NET DevelopersiosForDotNetDevs.comPaperback, iBooks, Kindle, Nook

WHY MOBILE?

Huge demand for mobile devs

Large budgets for mobile projects

Lots of greenfield dev work! :-)

WHY IOS?

Not the only choice, but a good one

Many mobile projects focus on iOS

Perceived difficulty == Mo’ Money

IOS APP PLATFORMS

Xamarin/MonoTouch - C#

PhoneGap - HTML/JavaScript

Native - Objective-C

MY FIRST REAL IOS PROJECT

TRANE MAP

For HVAC salespeopleSelect systems to sell

Present systems to homeownerCreate and sign proposal on iPad

Generate PDF proposal document

VIDEO

Trane MAP via Cynergy.com

LESSONS LEARNED

Mobile apps are a different breedMobile form factor matters

Apps can (easily) run out of memoryNaming conventions are important

Core Data is terrificBe careful re: data model versioning

NOT IN KANSAS ANYMOREWindows OS X

Visual Studio Xcode

C# or VB.NET Objective-C

Garbage Collection Reference Counting

.NET Runtime Objective-C Runtime

Base Class Library Foundation

WPF or SL or WinForms UIKit

TOUR DE XCODELet’s take a guided tour of Apple’s IDE...

OBJECTIVE-C != C#

OBJECTIVE-C

Superset of C

Object orientation a la Smalltalk

Obj-C Runtime supports OO

POINTERS 101

Pointer is 8 bytes of memory

Stores a memory address

Not guaranteed to be valid

POINTERS EXAMPLE

int *pointerToInt = NULL;int someInt = 42;// Assign the pointer the address of someInt.

pointerToInt = &someInt;// Dereference the pointer and assign it a value.

*pointerToInt = 101;assert(someInt == 101);

NIL / NULL

nil - for pointer to Obj-C objectNULL - for pointer to C valueNSNull - similar to .NET DBNullNil - for pointer to a Class object

NIL HANDLING

nil is false and non-nil is trueif (aPointer != nil)...is equivalent to...if (aPointer)

CALLING A METHOD

Obj-C “message passing”[anObject someMethod];C#anObject.SomeMethod();

MESSAGE TO NIL

Messages sent to nil are ignored

Evaluates to default of return type (0)

Edge cases if method returns C struct

PASSING AN ARGUMENT

Obj-C[dev learnSkill:@”iOS”];C#dev.LearnSkill(”iOS”);

PASSING ARGUMENTS

Obj-C[obj setOffset:42 animated:YES];C#obj.SetOffset(42, true);

CREATING AN OBJECT

Obj-CJASFoo *f = [[JASFoo alloc] init];JASFoo *f = [JASFoo new];

C#Foo f = new Foo();

.H & .M FILES

Classes are split between two files

Header (.h) - declarations

Implementation (.m) - definitions

CLASS DECLARATION

Obj-C (in .h file)@interface JASFoo : NSObject- (BOOL)hello;@end

C# does not have an equivalent

CLASS DEFINITIONObj-C (in .m file)@implementation JASFoo { NSString *_anIvar;}- (BOOL)hello { return NO; } @endC# (in .cs file)public class Foo { private string _aField; public bool Hello() { return false; }}

METHODS

Declared in .h file (optional)Defined in .m file

Class methods prefixed with +Instance methods prefixed with -

CLASS METHODS

Similar to static methods in .NETCan be overridden by subclasses!!!Template:+ (return_type)methodName:(arg_type)argName

Example:+ (JASFoo *)fooWithURL:(NSURL *)url;

INSTANCE METHODS

Template:- (return_type)methodName:(arg_type)argName

Example:- (int)indexOfObject:(id)anObject;

PROPERTIES

Declared in .h@property (nonatomic, copy) NSString *name;

Synthesized by compilerCustom accessor methods in .mExample usage:obj.name = @”Arthur Dent”;

THE SELF POINTER

Similar to ‘this’ in C#

Points to object in instance methods

Points to a Class in class methods

THE SELF POINTER

Obj-Cfloat f = [self instanceMethod];double d = self->_anIvar;

C#float f = this.InstanceMethod();double d = this.aField;

OBJECT INITIALIZERLike a constructor in .NET- (id)init { self = [super init]; if (self) { // Assign initial values. _anIvar = 42; } return self;}

DEALLOC

Called before an object is killed- (void)dealloc { [_anIvar cleanUp]; // Only if ARC disabled... [super dealloc];}

MEMORY MANAGEMENT

MEMORY MANAGEMENT

No Garbage Collector

Reference/Retain Counting

Automatic Reference Counting (ARC)

OBJECT OWNERSHIP

Objects live while owned

Owned == Retained

An owner retains an object

OBJECT OWNERSHIP

Deallocated when retain count is 0

Deallocated immediately by runtime

Pointer to dead object is “dangling”

NSOBJECT +ALLOC

+alloc

Allocates new object

Initial retain count of 1

NSOBJECT -RETAIN

-retain method

Increments receiver’s retain count

NSOBJECT -RELEASE

-release method

Decrements receiver’s retain count

If retain count reaches 0 object dies

NSOBJECT -AUTORELEASE

-autorelease method

Delayed decrement of retain count

Used when returning a new object

NSOBJECT -DEALLOC

-dealloc method

Relinquish ownership of objects

Invoked when retain count is 0

EXAMPLEFoo *f = [[Foo alloc] init];// f’s retain count is 1[f doSomethingAwesome];[f release];// f’s retain count is 0// f’s -dealloc executesf = nil;// Assign nil to avoid dangling pointer

ARC

Compiler feature

Adds memory mgmt to your code

Introduced in iOS 5

EXAMPLE WITH ARC

Foo *f = [[Foo alloc] init];[f doSomethingAwesome];

FOUNDATION VS. BCL

OBJECT VS. NSOBJECT

STRING VS. NSSTRING

STRINGBUILDER VS. NSMUTABLESTRING

DATETIME VS. NSDATE

ARRAY VS. NSARRAY

HASHTABLE VS. NSMUTABLEDICTIONARY

UIKIT

UIKIT

High-level user interface API

Provides the “iOS look & feel”

Based on MVC pattern

DRAWING SYSTEMS

VIEWS

UIView is the basic UI object

Views can contain subviews

Views are contained by a superview

UIVIEW SUBCLASSES

UIButtonUILabelUITextFieldUIImageViewUITableView

VIEW CONTROLLERS

Manage a set of Views

Container controller (manages controllers)

Content controller (displays stuff)

CONTAINER CONTROLLERS

UINavigationControllerUITabBarControllerUIPageViewControllerUISplitViewController (iPad only)

CONTENT CONTROLLERS

UITableViewController subclasses

Your UIViewController subclasses

MODAL PRESENTATION

Controllers can be ‘presented’

Presented controllers are ‘modal’

Modal controllers are ‘dismissed’

PRESENTATION EXAMPLE

XIB FILE

Contains a View

XML data

Edited via Interface Builder

STORYBOARD FILE

Contains multiple Views (“scenes”)

Defines navigation paths (“segues”)

Edited via Interface Builder

OUTLETS

A property or ivar on a Controller

Assigned a View pointer automatically

Hooked up in Interface Builder

ACTIONS

UI event handling methods

Defined in Controller classes

Hooked up in Interface Builder

LET’S WRITE AN APP!

Create View with Interface BuilderAdd outlets and action to Controller

Concatenate two NSStringsDisplay calculated value in View

SUMMARY

Different terms, similar ideasXcode is Apple’s free IDE

Objective-C is (kinda) like C#Foundation contains common classesUIKit and Interface Builder create UIs

There is a lot more to know...

LEARN MORE

iosForDotNetDevs.com‘iOS Programming for .NET Developers’

Q&A